高分子材料在經由gamma-ray照射之後，會使得高分子原有的性質發生變化，像是機械、光、熱、化學性質等等，然而本篇論文將著重於高分子在高溫時，其硬度的變化機制以及自由基的產生。高分子的硬度會隨輻射所產生的缺陷而有所變化，至於自由基的形成主要是因為高能量的gamma-ray打斷了高分子內部的鍵結，所以才導致自由基(free radicals)的產生。
此實驗是利用鈷-60作為輻射源的加馬射線去照射常見的工程塑膠Polyoxymethylene (POM)，並且以輻射後的POM高分子作為研究材料。然而本論文內容分為兩部分，第一部分，探討硬度在不同的退火溫度其硬度隨時間變化，第二部分則是運用Electron Paramagnetic Resonance (EPR)所量測到的光譜，透過WINEPR、SimFornia和WinSim2002等專用軟體，模擬分析所產生的自由基種類及演化。
根據實驗結果，經過加馬射線照射的POM，在40, 60, 80, 100℃這四種不同的退火溫度下，其硬度都會隨時間有明顯的上升，除此之外，照射劑量的提高會導致硬度下降。然而在高溫中，硬度隨時間的增加是一種零階和一階混合的動力學過程。電子順磁共振光譜的部分，依據我們所摸擬出來的光譜，輻射後的POM主要會產生四種自由基，分別是 ˗OCH2• 和˗OĊHO˗ 以及 ˗CH2O• 還有 HOO• ，但是與硬度不同的地方，在於其光譜會隨時間增加，有顯著的衰退，至於加馬射線劑量的增加則會使光譜強度上升。

After Co60 gamma-ray irradiation, the polymer materials will change their mechanical, optical, thermal, and chemical properties. Then this thesis focuses on the evolution of hardness and chemical reactions at elevated temperature. The hardness of polymer is controlled by the defect induced by the gamma-ray irradiation, and the irradiated polymer also generates free radicals since the high-energy particles break the chemical bond of the polymer.
In this experiment, the polyoxymethylene (POM) specimen was irradiated by Co60 gamma-ray. The study is divided into two parts, one is the evolution of hardness during different annealing temperatures, and the other is the Electron Paramagnetic Resonance (EPR) spectra using computer software WINEPR, SimFornia and WinSim2002.
We found the hardness of irradiated polyoxymethylene increases with annealing time. The hardness reduces when gamma-ray dose increases. The annealing of defects which affect the hardness follows a mixture of zeroth order and first order kinetic processes. The EPR spectra of irradiated POM are possibly attributed to four radicals, which are ˗OCH2• as radical Ra, ˗OĊHO˗ as radical Rb, ˗CH2O• as radical Rc and HOO• as radical Rd, respectively. Electron Paramagnetic Resonance spectra decrease with increasing time and the intensity increases when gamma-ray dose rises.

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